Nozzle for expansion and compression of gases



Jan. 19, 1954 J. A. CHALOM NOZZLE FOR EXPANSION AND COMPRESSION OF GASES Original Filed Jan. 17, 1949 Patented Jan. 19, 1954 I fXPANsIo AND COMPRES- sIoN 0F GASES iIosephAron Chalom, Paris, France original application January 1'7, 119419, ssn alno. "71;ss9,-novg,-Patpj1jt No. "2,583,726, cared Jamary .9 1952-. Minded and this application 7 Claims .priioi ity, ap jlica'ti on France January 26, 1948 TGlaim.

This application "is a fdivision o'f agp'lica'tion Serial No. 71,339, filed January 1'7, 19-49, noyv Patent No. 2,583,726, granted January 29, 195-2. This invention relates "to nozzle for the -ex- 'pans'ion and compression of gases and "vapors, such 'as for instance the nozzles of supersonic ejectors. I

It i's an object of this invention to provide no'z- "zles 'of "'the kind indicated above, in which the losse of energy arereduced'to a minimum.

The invention is based "on the following findmgs: I

'ftfa gas jet "carryingsharp and abrasive-particles such as sand grainsjis injected into a cylindr'ical bore, for instance by replacing the nozzle of a sand blast'apparatus "byja metal piece ror m'ec :Witha pylin'diical' b'OI, ibiWillb found thcit there is quickly termed "a holiow'revolution surface witha concave profile 'iaeing 'the axi and which at "a certain distance from the entrance of the U bore "attains a'maxirnum diameter which merges into contracted and expanded sections. The length of the bore mans-diameter determine, an other "factors remaining constant, the "diameter at'each point 'ancithe "distance-from the entrance atiwhich'the largest diameter hollow is situated.

"If the hollowed-out piece is cut through at the largest diameter, there is obtained "a 'nozzle'the profile or "which is concave toward the 'a'xi and isio'ined "by means of an angular profile in its narrowest'sec'tion with a. "rounded part of "a niinimm diameter only *a little greater than that of the bore. n concave profile of this kind enables the streams of fluid "expanded at maxi- "mum speed at the maximum section totravel in mm-island thus to reduce theshocks to a minimirm.

the neck of the nozzle Wherethecross-secthelowest, while the speed of the fluid comes cicsest to the 'velocitynf sound, the profiles are joined along an angular profile with "a tangent angle at the maximum of more thanlO tor-iii up to "l fs degrees. ty e of profile, obte ined his the auto'matic "-holiow'ing of the piece by asand ifla'st or the like differs definitely from theioustomary pr'o'fiies which as a r-me openiii-g cones of only about *7 degrees :aare used. The new'nrofiie of iar more rapid evolution leads. to shorter nozzles; which is advantageous. making use :of these facts, and by systematic eiiperimenitin'g it becomes possible to calculate the elements 11f :dianneter :andJ-engthof the here to he rshtained predetermined cases; 7

The production of such a profile andfits' 21-p- :plicaztions are iiiustrat'ed 'diiiigiafiimatial-ly by way-of example "in the drawings aifi'xed 'to this specification andforrnin'gpart thereof.

Inthe drawings c Fig 1 is an axial section of a nozzle blank de- 5, signed tobe subjected'to theholloWing-outtfatment according-tothe invention. I

Fig. 2 is a similar view of a blank fitted With an auxiliary piece before being treated.

Fig.3 is the finished nozzle.

Fig. 4 is 'an axial section of an ejector fitted with an expansion and a super-sonic Compression nozzle. V v

Fig. 5 illustrates the adaptation of "thconca've profile according to theihvent'ion to 'a"ri*111ltistag"e nozzle. 7

Fig. 6 shows ahlaiik "for the production of'siibsonic nozzles according to the invention by means of a modified treatment accordin to the invention, and

Fig. '7 shows a compression nozizl'e in which a super-sonic element of concave profile is "combined with a sub-sonic expansion nozzle 1ir0- dueed in accordance with the invention.

Referring to the drawings and first to Figs. 1 and 2, Fig 1 shows a blank A of dimensions approximately calculated for the nozzle to be produced, beingfla cylinder 1 with threaded "endpieces 2 and :3 of smaller diameter which serve for the provisional and the permanent mounting in place of the 'blank 'and the finished nozzie, respectively. The two threaded endldiec'esiir'fig h-t of course be replaced by some other fixatiiih means. Thefthr'ead 3 is so chosen that the diameter at the bottom of the thread is equa to the diameter of the exhaust end of the nozzle to be produced. An auxiliary cylinder B 'of'ab'out equal i'eng'th is screwed down on the endpiece sand the two united'cylinders are now bored axia11y; the diameter of the bore 'beih'g 'slightly smallerthan n the neck of the nozzle. The united pieces are then mounted b th' threaded ehdp'ie'ce in the exhaust of a sand blower which is noW-staft'e'd running. The Said blast passing through the bore hollows out the bore until the inner diameter of the bore in the end'p lane C of 'thebody A becomes equal to the diameter of the 'e'n'dpi'ec'e '3. When this point is reached, the auxiliary cylinder drops and the blower is shut off. The body A is novv hollowed out according to the aim file 5, which is the one desired, being concave towards the nozzle axis in its super-sonic section and'havihg, in the sections corresponding to the highest velocities, tangents substsntia'l'iy caramel 7 t0 the axis, While fol velocities 'fiar sound V- locity, near the neck of the nozzle, the tangents temperature of the gases flowing through the nozzles.

The end of each operation is indicated automatically by the dropping off of the auxiliary cylinder B. The nozzle A can then be finished by filing the outer edge of the exhaust end and bringing the diameter of the neck to the exact measure required.

The ejector shown in Fig. 4 is formed with nozzles of concave profile serving for ejecting air or steam from condensers or other apparatus. It comprises a steam intake compartment H, a super-sonic expansion nozzle [2 with concave profile, a suction box 3, a super-sonic compression nozzle M with concave profile and a subsonic diffuser 5. The end of the nozzle i2 is beveled and placed somewhat to the inner side of the intake end of the nozzle It.

Owing to their concavities facing the axis of the nozzles, the profiles according to the invention offer a great variety of inclinations towards the axis, starting from a maximum at the neck to their disappearance at the widest opening, and allowing to obtain, by an association of such different profiles, a general profile which presents angle points with an angle of more than and up to degrees between the tangents on these points, common to two profiles. This is in direct contrast to the conventional profiles hitherto used which allowed only minute changes of inclination between two profiles which were themselves little inclined and lacked any valuable inclinations. Obviously this is an important result of the use of concave profiles according to the invention.

If a nozzle is for instance used for an expansion of steam to a predetermined lower pressure, it is known that, if this pressure rises, while all other conditions remain unchanged, the adhesion of the steam jet to the wall will cause the expansion to be lowered to a value which may be very much lower than the pressure which then obtains effectively, and that this expansion will be followed by a sudden recompression by shock wave, all this resulting in considerable losses of kinetic energy.

Since industrial apparatuses fitted with expansion nozzles must be able to function under more or less considerable changes of working conditions, such nozzles are as a rule made shorte than the length theoretically corresponding to mean conditions. However, if the loss of output sufiered by a rising of the expansion pressure above these conditions is avoided, there exists another cause for losses by the undulat-ory flow at the exhaust when the expansion pressure is lower than the mean conditions of operation. These losses can also attain an important value.

In order to avoid these inconveniences, the combination of super-sonic concave profiles according to this invention allows me to give to the general profile of the nozzle a discontinuous curvature by abruptly varying the value of the angle of the tangent at the profile relative to the nozzle axis from its minimum value to its maximum value. One thus obtains a discontinuous profile composed of two or more curves opening towards the axis, the points where the diiierent curves meet, being characterized by a double value of the angle of the tangent on that point, one being substantially zero, the other one for instance 15 degrees. The angle points which are thus obtained between a certain number of sections of a nozzle corresponding to a certain number of exhaust conditions, by favoring the separation of the gas currents from certain values of exhaust conditions on, allow me to obtain, from the best adapted section on, parallel exhaust. This parallel exhaust fiow then passes without any inconvenience through sections of larger diameter which have not much to do with the functioning of the nozzle. The figure shows schematically such an operation under conditions arising between the maximum pressure drop corresponding to the first element alone and the minimum pressure drop corresponding to the entire nozzle. This solution was not possible with the conical profiles of low angle apex in which one would have been limited to an insignificant change of angles. The solution thus results directly from the type of profile obtained by the method of fabrication according to this invention.

Fig. 5 illustrates diagrammatically the expansion nozzle of a steam ejector, according to the invention, in which the parts of which it is composed, are assembled by means of screw threaded sections machined as perfectly as possible so that the adjoining profiles merge into one another as perfectly as possible. The number of parts is a function of the range of aspiration pressures to be obtained, but it may also be dictated by the machining facilities available. Experiencehas shown that if the maximum section exceeds four times the minimum section, the period of tim required for machining the profile of the nozzles by way of sandblasting as indicated above begins to become prohibitive. It is therefore advisable to compose the nozzle of the number of pieces which is closest to the quotient by 4 relative to the maximum and minimum sections of the entire nozzle.

Obviously, since the method according to the invention produces a concave profile of a novel type, it might be possible to produce by less economical machining methods of the classical kind nozzles which might come near to the profiles accordin to the invention, no matter whether the profile is simple or, as explained above, composed of a series of concave elements succeeding each other by definite angle points, corresponding at the parallel exhaust to the axis of a profile extended by the adjoining part, open at 20-30 degrees, of the next following profile.

Without departing from the invention, it is also possible to utilize modified forms of proceeding for the production of rather short concave profiles, for which the method according to the invention furnishes automatically the profiles with continuously varying curvature-as explained above, which are useful for super-sonic expansion nozzles.

It is for instance possible, by laying down all the elements of importance in machining, such as the properties of the metal, the kind and size of the abrasive matter, the air pressure, the diameter and length of the section to be reamed, to synchronize the period of time required for obtaining a nozzle of the desired profile. Once this period has been established by tests, it will be suflicient to stop the sand blast at the end of this period. The concave profile with parallel gas exhaust is then obtained again and again without the necessity of a drop of material as in the modification first described.

On the other hand the method according to this invention, by facilitating the hollowing out of the blanks, enables long profiles corresponding to sub-sonic velocities to be fabricated automatically. To this end a blank of the desired length may be pierced, not by a cylindrical bore, but by a hollow constituted by a plurality of coaxial cylindrical bores T1, T, T3 (Fig. 6) of increasing diameters which succeed one another within the central section of the blank. The length L1, L2, L3 and the diameters of these cylindrical borings will be determined by tests or empirically.

Under these conditions there is obtained with the aid of the grinding blast a continuous oblong profile which closely follows the desired profile, and by synchronisation or by any other means announcing the end of the fabricatin period, oblong sub-sonic profiles can be produced.

By combining, as shown in Fig. 7, a supersonic diffuser F of concave profile with a subsonic diffuser E of oblong profile, a diffuser is obtained which will be capable of compressing a flowing gas from super-sonic velocities down to a velocity approaching zero.

The new method can be carried through with the aid of any suitable fluid, besides compressed air, for instance steam, and with any other suitable abrasive matter, besides sand. The form of the jet may be changed during operation, for instance near the end.

Various changes may be made in the performance of this invention and in the means employed for this purpose without departing from the invention or sacrificing the advantages thereof.

I claim:

A tubular multistage nozzle comprising as part of its boring a plurality of supersonic exhaust portions of concave profile in relation to the nozzle axis, arranged in series, said inlet portion having a substantially conically converging axial section ending in a throat having the smallest cross-section of the nozzle, the first exhaust portion which extends from said throat in the direction towards the exhaust end of the nozzle, having a profile concave in relation to the nozzle axis and being so formed near said throat that the tangent to it, starting from said throat, encloses with the nozzle axis an angle rangingbetween about ten and fifteen degrees, the second exhaust portion arranged in series with said first one having a profile concave in relation to the nozzle axis and starting with a cross-sectional area of passage about equal to the cross-sectional area of the end of said first exhaust portion, the tangent of the first part of said second exhaust portion enclosing with the nozzle axis an angle ranging between about ten and fifteen degrees and the tangents to the successive sections of said second exhaust portion enclosing with said axis successively smaller angles.

JOSEPH ARON CHALOM.

References Cit-ed in the file of this patent FOREIGN PATENTS Number Country Date 392,826 Great Britain May 25, 1933 485,322 Great Britain May 18, 1938 

